Report on the Earthquake: 18 km SE of Miyazaki, Japan¶
General Information¶
- Date and Time: 13 January 2025, 12:19:32.81 UTC
- Magnitude: 6.6 (from local catalog)
- Location: The earthquake occurred offshore, approximately 10 km from the Miyazaki coastline (Fig. 1).
Focal Mechanism and Fault Analysis¶
Based on the focal mechanism solution provided by GCMT, the faulting is reverse, consistent with the tectonic style of the region.
An analysis of the active fault plane conducted within one hour of the M6+ occurrence reveals only one event difference between the active and auxiliary planes, reducing the reliability of the active plane selection. Extending the analysis window to 12 hours increases the number of events on the active plane to 5 (Fig. 2).
Seismicity and b-value Analysis¶
The seismicity map for the period 13–14 January shows a noticeable spatial separation between the M6+ and the minor seismicity. While a cluster of low-magnitude earthquakes is observed, it is located several tens of kilometers eastward and falls outside the box corresponding to the active fault plane. This displacement makes it impossible to estimate the post-M6+ b-value time series (Fig. 3).
From 2012 to 13 January 2025 (the date of the M6+ event), 238 events were recorded within the box associated with the active fault plane (Fig. 4). The pre-M6+ b-value for this region is estimated to be 0.84. The valid events currently available for calculating the post-M6+ b-value time series are only 3 (Fig. 5) and are insufficient to establish any reliable status.
Figure 1: Generic map of the area with the location of the earthquake¶
Figure 2: Bar chart for active fault plane selection¶
Figure 3: Seismicity map of the area for the events that occurred in the 3 days after the M6+¶
